The present invention relates to a floating die-type powder press and more specifically to means for stopping and releasing its floating punch.
Some powder presses employ a plurality of punches in order to form compacts of varying heights, flange thicknesses, etc., by means of the same die set. Such presses comprise a die proper, and one or more lower punches to impart a desired bottom contour to the compact, together with or without a core rod to create a central bore in the product.
In such powder presses the powder material is compacted in the cavity of the die set by the descending upper punch. The die, lower punches, and core rod are maintained in their preassigned relative positions by appropriate stop means during the compaction of the material. The compacted product is ejected out of the die cavity with the stop means held inoperative. During the ejection of the compact the stop means are unlocked by and set free from their locking members when the compact is ejected to such an extent that the top surfaces of the lower punches become coplanar with that of the die. Thereafter the lower punches and the die are lowered, with their top surfaces maintained in coplanar relationship with each other, to the final position where the product is withdrawn.
Although a variety of stop devices have been suggested, each has a problem in regard to reliability of operation, ease of manufacture, and size. No truly satisfactory device has been available.
Conventional stop devices comprise either stop slides with planar load-bearing surfaces, bell cranks, or wedges, which are all engaged and disengaged to stop and release the floating punch or punches.
The stop device with the bell cranks is such that the bell cranks are pivotally mounted to a plate carrying a floating punch. The bell cranks bear the loads by abutting against fixed supports and are disengaged therefrom as a pusher pin acts on one of the arms of each bell crank. Because of the pivotal motion of the bell cranks, however, their pivot portions and surfaces of contact with the fixed supports must be curved, and their load-bearing surfaces make line contact with the supports. Thus, by reason of their low rigidity, the bell crank-type stop device is not suitable for high pressure presses.
The stop devices with the planar stop slides and wedges are more stable structurally and so capable of bearing greater loads. However, since the stop slides or wedges must travel laterally on their stationary support for disengagement, they require considerable space for such lateral displacement. Further the wedge-type stop device is mechanically complex and demands large space in the press, causing a decrease in its rigidity. The press will become expensive if its parts are made stronger to compensate for such decreased rigidity. Because of its large size, moreover, it lends itself to use with presses having no more than two floating punches.